Conventionally, hybrid vehicles, electric vehicles and the like have been known that run by driving force of an electric motor. These vehicles have a battery mounted thereon for storing electric power to be supplied to the electric motor serving as a driving source.
Japanese Patent Laying-Open No. 8-37703 discloses a hybrid electric vehicle including a battery charged by an outside charger, a driving motor for driving wheels by electric power from the battery, an engine used indirectly for driving the wheels, a control unit for controlling operations of the motor and of the engine, and a determination unit for determining whether the battery meets prescribed specifications. When means for determining battery specifications determines that the battery does not meet the prescribed specifications, the control unit controls at least one of the motor and the engine to limit output of the driving motor.
In order to increase a distance that can be traveled on a single charge, it is conceivable to increase a capacity by increasing the number of power storage mechanisms, such as batteries, mounted on a vehicle. When a plurality of power storage mechanisms are mounted on the vehicle, however, charging conditions of all the power storage mechanisms may not necessarily be equal. For example, sufficiently charged power storage mechanisms and insufficiently charged power storage mechanisms may both be present, so that states of charge and the like may vary among the power storage mechanisms. The varying states of charge and the like among the power storage mechanisms may result in varying rates of deterioration among the power storage mechanisms. However, Japanese Patent Laying-Open No. 8-37703 does not provide any descriptions about such a problem.